In recent years, Quality of Service (QoS) technology has been considered as a technology that guarantees communication service quality of real time communications such as Internet telephone, VOD (Video on Demand) service, or the like. QoS technology is used by a relay apparatus which relays a content in a communication path between a communication request apparatus utilizing contents, and a server (hereinafter, referred to as a destination apparatus) providing the contents. For example, a standardized QoS technology for a relay apparatus used in a wireless LAN (Local Area Network) is established by IEEE (Institute of Electrical and Electronics Engineers) 802.11e standard. In addition, the Homeplug alliance has been put to practical use of a QoS technology for a relay apparatus used in PLC (Power Line Communications).
In real time communication, in order to prevent disposal or delay of a packet, a relay apparatus reserves a bandwidth necessary to transmit a content in a communication path, and guarantees a constant communication speed. As a result, services that cannot tolerate delays or terminations of communication, such as video telephone and real time transmission of audio or video, can be transmitted by being given priority over other services (e.g., patent literature 1).